Dan Rhodes has made his name with a collection of highly original novels, from Timoleon Vieta Come Home and Gold, to Little Hands Clapping.

Like hot fat in a pan, he is unpredictable, jumping from one tack to another in each of his books. Not for him an easy label, or a sure place on any genre shelf. All that remains constant is a brightness of tone, a whimsical take on the world, and very probably a macabre or sombre twist.

On those fronts, This Is Life does not disappoint. Those who like kookiness will, in fact, be delighted. From the outset, Rhodes sets in motion a carousel of giddy events, employing a cast of wilful eccentrics who are no doubt the only folk he could persuade to take part in the rollicking foolishness of much of this plot.

Taking Paris as its stage, This Is Life is many things: a romance, a satire on the modern art scene, a paean to babies and an off-the-wall but feeling reflection on the meaning of life at its most biological. Its central character is art student Aurelie Renard, who comes up with a daft notion for a project to impress her professor, in which she'll throw a stone in the air. Whomever it lands upon will become the subject of a week-long scrutiny, out of which she hopes to produce great mixed-media art.

Things go bad from the start when the stone lands on a baby, whose carer promptly hands him over to her for a week to look after: a week in which, among other things, Aurelie accidentally (but not fatally) shoots him, and falls in love with a mysterious, globally renowned performance artist known as Le Machine. His schtick is to spend 12 weeks confined to a stage, collecting the excretions he produces in that time. Critics hate the show, and the public loves it.

As a broadside against the pretensions of the art world, This Is Life is savage. The brilliantly sneering arts journalist Jean-Didier Delacroix is one of Rhodes's tours de force, a man so vilely opinionated the page lights up whenever he appears. On the other side of the art coin – and every bit as aware of its meretriciousness – is Le Machine, the true hero of the story. As he reflects, "If it hadn't been for people like his manager, if it had been run solely by artists and born-wealthy dilettantes, the art world would never have been anything more than a hotbed of intrigue, failing livers, lost fortunes, unfulfilled potentials and herpes."

At 400-plus pages, this is the longest and, to my mind, least engaging of Rhodes's novels. We are far into the story when he quotes Goethe: "Art and life are different; that is why one is called art and one is called life." But as this fiction shows, This Is Life is anything but; the artifices of Rhodes's trade could scarcely be more pronounced, from crazy coincidences, narrow escapes and happy endings, to characters so much larger than life they make the Eiffel Tower look like a matchstick.

All of these would be fine, were it not for the flatness of the writing. Every so often Rhodes's pin-sharp prose kicks in, and the result never fails to amuse. But for long stretches he flirts perilously with the inane and the obvious. On this evidence, whimsy is an attribute that works well in the sprint, but not over the long haul, where what was charming begins to feel laboured. As the best of Rhodes's writing in this novel shows, economy is crucial to his style of wit.

As is a strong sense of humanity. At its heart, as with much of Rhodes's work, there is a story that matters, a kernel of true substance. It is this, in the shape of Le Machine, which transforms This Is Life from just a clever fictional circus and slapstick satire, into something more affecting and significant.

This Is Life

Dan Rhodes

Canongate, £12.99